U.S. Pat. No. 5,494,609 discloses an electrically conductive coating composition comprising: a dispersion comprising dispersed particle of an intrinsically conductive polymer and, a solution which comprises a hydrophobic film-forming thermoplastic polymer, a highly polar plasticizer, and, an acid anhydride surfactant, in an organic solvent; wherein said thermoplastic polymer is soluble in said solvent to at least 1 percent by weight; and, wherein said dispersion comprises from about 1 to about 50 percent by weight of said intrinsically conductive polymer.
EP-A 440 957 discloses dispersions of polythiophenes, constructed from structural units of formula (I):
in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together form an optionally substituted C1-4-alkylene residue, in the presence of polyanions.
EP-A-686 662 discloses mixtures of A) neutral polythiophenes with the repeating structural unit of formula (I),
in which R1 and R2 independently of one another represent hydrogen or a C1-4-alkyl group or together represent an optionally substituted C1-4-alkylene residue, preferably an optionally with alkyl group substituted methylene, an optionally with C1-12-alkyl or phenyl group substituted 1,2-ethylene residue or a 1,2-cyclohexene residue, and B) a di- or polyhydroxy- and/or carboxy groups or amide or lactam group containing organic compound; and conductive coatings therefrom which are tempered to increase their resistance preferably to <300 ohm/square.
WO 99/34371 discloses a screen paste with a viscosity of 1 to 200 dPa·s (102 to 2×10 mPa·s) containing a solution or dispersion of a conductive polymer paste and optionally binders, thickeners and fillers. WO 99/34371 further discloses a process for preparing screen pastes in which a solution or dispersion with a content of <2% by weight of poly(3,4-ethylenedioxythiophene) [PEDOT]/poly(styrene sulphonate) [PSS] is concentrated to a solids content of >2% by removing the solvent and in which subsequently binder and/or filler are optionally added. Example 1 discloses evaporation of water from a 1.3% by weight solids dispersion of PEDOT/PSS in water to a 3% by weight solids dispersion in a rotary evaporator at 45° C. and 20 mbar.
EP-A 1 081 549 discloses a coating composition comprising a solution of a substituted or unsubstituted thiophene-containing electrically-conductive polymer, a film-forming binder, and an organic solvent media; the media having a water content of less than 37 weight percent. Coating dispersions with 0.1% by weight of PEDOT/PSS, i.e. 0.0294% by weight of PEDOT since BAYTRON® P contains a weight ratio PEDOT to PSS of 1:2.4, and with between 8 and 25% by weight of water were disclosed in the invention examples using BAYTRON® P, a 1.22% by weight dispersion of PEDOT/PSS in water, as the starting material.
EP-A 1 081 546 discloses a coating composition comprising a solution of an electrically-conductive polymer and an organic solvent media wherein the solvents are selected from the group consisting of alcohols, ketones, cycloalkanes, arenes, esters, glycol ethers and their mixtures; the media having a water content of less than 12 weight percent. Coating dispersions with PEDOT/PSS concentrations between 0.02 and 0.1% by weight, i.e. between 0.00588 and 0.0294% by weight of PEDOT since BAYTRON® P contains a weight ratio PEDOT to PSS of 1:2.4, and with between 2 and 8% by weight of water were disclosed in the invention examples using BAYTRON® P, a 1.22% by weight dispersion of PEDOT/PSS in water, as the starting material.
EP-A 1 081 548 discloses a coating composition comprising a substituted or unsubstituted thiophene-containing electrically-conductive polymer and an organic solvent media; the media having a water content of less than 12 weight percent. Coating dispersions with PEDOT/PSS concentrations between 0.02 and 0.1% by weight, i.e. between 0.00588 and 0.0294% by weight of PEDOT since BAYTRON® P contains a weight ratio PEDOT to PSS of 1:2.4, and with between 2 and 8% by weight of water were disclosed in the invention examples using BAYTRON® P, a 1.22% by weight dispersion of PEDOT/PSS in water, as the starting material.
WO 02/042352 discloses a process for producing a water-dispersible powder essentially consisting of polymer particles T with repeating thiophene units and at least one further polyanionic polymer P characterized in that a dispersion or solution containing said polymer T is mixed with a compound which forms an azeotrope with water, the water is removed by azeotropic distillation and the polymer obtained isolated and dried.
WO 02/067273 discloses a method for exchanging solvent in a mixture comprising water and an optionally substituted polythiophene, the method comprising: a) heating at least one solvent in a vessel under conditions suitable for vaporizing water; b) contacting the heated solvent with the mixture comprising water and optionally substituted polythiophene, the contact being sufficient to remove at least part of the water from the mixture as vapor; and c) exchanging the water removed from the mixture with the solvent.
WO 02/072660 discloses a process for the preparation of dispersions or solutions, containing optionally substituted polythiophenes in organic solvents, characterized in that: a) a with water-miscible organic solvent or a with water-miscible organic solvent mixture is added to an aqueous dispersion or solution containing optionally substituted polythiophenes and b) the water is at least in part removed from the resulting mixtures. WO 02/072660 only exemplifies solvent exchange using N-methyl-pyrrolidinone (NMP) and dimethyl acetamide (DMAC).
WO 02/072714 discloses solutions and/or dispersions of organic semiconductors in a solvent mixture of at least two different organic solvents, characterized in that (A) each of the solvents on its own exhibits a boiling point below 200° C. and a melting point less than or equal to 15° C., (B) at least one of the solvents exhibits a boiling point between 140° C. and 200° C., (C) the solvents used do not contain benzylic CH2- or CH-groups, (D) the solvents used are not benzene derivatives, which contain tertiary butyl substituents or more than two methyl substituents.
For many applications it is desirable that the coating medium of the conductive polymer dispersion be largely non-aqueous to aid surface wettability and reduce the energy requirements for drying. However, to avoid excessive dilution of the conductive polymer, large coating thicknesses and excessive use of solvent, the concentration of conductive polymer should be as high as possible. This can be realized by diluting aqueous dispersions with organic solvents, but this results in extreme dilution of the conductive polymer to 0.00588 to 0.0294% by weight, as disclosed in EP-A 1 081 546, EP-A 1 081 548 and EP-A 1 081 549.
Aspects of the Invention
It is therefore an aspect of the present invention to provide a method of preparing a composition containing concentrations of conductive polymers of at least 0.08% by weight in a largely non-aqueous medium or an aqueous medium with a solvent concentration of at least 30 percent by weight.
It is a further aspect of the present invention to provide a coating composition containing concentrations of conductive polymers of at least 0.08% by weight in a largely non-aqueous medium or an aqueous medium with a solvent concentration of at least 30 percent by weight.
It is also an aspect of the present invention to provide a coating process for coating a composition containing concentrations of conductive polymers of at least 0.08% by weight in a largely non-aqueous medium or an aqueous medium with a solvent concentration of at least 30 percent by weight.
It is also an aspect of the present invention to provide a printing ink or paste containing concentrations of conductive polymers of at least 0.08% by weight in a largely non-aqueous medium or an aqueous medium with a solvent concentration of at least 30 percent by weight.
It is also an aspect of the present invention to provide a printing process for printing a printing ink or paste containing concentrations of conductive polymers of at least 0.08% by weight in a largely non-aqueous medium or an aqueous medium with a solvent concentration of at least 30 percent by weight.
Further aspects and advantages of the invention will become apparent from the description hereinafter.